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The Science of Hockey Ice

Illustration for article titled The Science of Hockey Ice

Hockey is a game played by linebacker-sized men moving at vehicular speed on razor-sharp blades. Skaters will travel almost 200 miles in a single game, slicing, shredding and shaving a surface just 200 feet long, 85 feet wide and 1 inch thick.

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The abuse the New Jersey Devils and Los Angeles Kings will heap upon their rinks during the Stanley Cup finals would pulverize a frozen lake, let alone the ice in your freezer. Yet the ice here at the Prudential Center will remain so smooth that a puck will slide over it with nary a untoward bounce.

Creating a rink suitable for the rigors of professional hockey is a feat of engineering, a lesson in chemistry and a work of art.

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"It's a living, breathing apparatus," Nick Kryshak, the Devils' official ice technician, said of the flawless polycrystal plane he's created. "It's not too hard, it's not too chippy, it's not too soft. Every little thing matters. You want that perfect consistency."

Achieving that perfect consistency is an arduous task. Building a sheet from scratch takes four days, with veneer-thin layers of water successively frozen and leveled in a carefully controlled climate.

Outside the Prudential Center in downtown Newark, less than 24 hours before Game 1, heat shimmered over the sidewalks and humidity draped like a wet towel. Inside, the arena was a nippy 50 degrees and the mirror-clear ice a frigid 20 degrees. Its clarity reflected its purity. The water used to create it passes through a truck-sized, eight-filter reverse osmosis system to remove excess oxygen and trace minerals, two enemies of ideal consistency.

Oxygen is what gives an ice cube its cloudy core. Too much of it softens ice, making skate blades sink and founder. It's the same story with minerals - total displaced solids, in technician argot. Too much softens the ice, but too little hardens it, making traction difficult. Kryshak will sometimes add baking soda until the balance is right.

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When the water is purified and primed, it's sprayed onto a concrete slab that rests on a labyrinth of pipes 9 miles long. Chilled salt water, which has a lower freezing point than fresh water, flows through the pipes, lowering the slab's temperature to 16 degrees Fahrenheit. That's cold enough to flash-freeze a layer of water precisely measured at 1/32 of an inch thick. Speed is essential.

"The more time you allow water to sit and freeze, the dirtier it gets," Kryshak said.

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Much like plywood, layers of ice create strength and density. The first layer is called a bond, and it is painted bright white. Lines and logos are all placed in the first eighth of an inch.

Kryshak isn't yet using the Zamboni, hockey's iconic icemaking vehicle, but walks back and forth with a spray wand and water tank for eight hours. Only when the ice is a half-inch thick do the Zambonis come out, depositing more 1/32″ layers and scraping uneven patches level.

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All told, Kryshak and his crew will spend four days laying down a sheet 1 inch thick, using sonar depth guns to ensure consistency across its surface. During the playoffs, when overtime can keep players on the ice into the wee hours and grind a standard sheet down to the concrete, Kryshak's team builds the ice to a depth of 1.5 inches.

The full bottom-to-top process will occur only a few times in a season - during basketball games and concerts the ice is simply covered, though a March circus visit and the threat of animal droppings necessitated a full rebuild - but maintenance is constant.

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After every game and practice, Kryshak's crew will spend two hours working on the ice, fixing damage or flaws they hadn't noticed. Each morning, even if the ice hasn't been touched, they shave off the top layer and add a new one: Over the previous night, the arena's dry air - kept at 35 to 40 percent humidity - will have drawn impurity-laden moisture to the surface.

Come game time, Kryshak's team concerns itself with on-the-fly care. They measure temperature, relative humidity and dewpoint at ice level, instructing ventilation engineers to pull air into the rink or blow it out as needed. The ice surface is kept at steady 19 to 20 degrees, while the arena stays between 50 and 60 degrees. Humidity is allowed to rise gradually, perhaps to 50 percent by a game's end.

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"When you run the dehumidifiers too much, you dehydrate the sheet," said Kryshak. "You cause it to be brittle."

Zambonis provide finishing touches, scraping away shavings cut by players' skates, removing the deeply scored top layer and resurfacing the rink with a fresh sheet of water 1/32" thick. Even this seemingly simple task requires near-perfect coordination.

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Most community rinks use a single Zamboni, but the pros use two. That cuts the flooding time in half, buying a few more minutes for fresh ice to settle, but the machines must be identically calibrated. Any variation between them creates minute ridges that might cause a puck to bounce or a skate to slip. For want of a mere millimeter of ice, a game could be lost, a series changed.

"The process is long. It's tedious. It takes a lot of patience," Kryshak said. "But it's all worth it in the end when you get to this stage of the game. You're in the Stanley Cup final."

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Image by Vaclav Volrab/Shutterstock


Illustration for article titled The Science of Hockey Ice
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DISCUSSION

I worked in a hockey rink for 10 years making and maintaining ice. It's a pretty cool (no pun intended) thing to see. It does not take 4 days to make playable ice. It can be done in two days if someone is there at all times. A few fun facts not mentioned in the article:

- The ice is painted white so the puck stands out on the surface. They started painting it white in the early 50's when games were being broadcast on TV. Black and white TV's meant the puck was hard to follow on a grey surface.

- You do machine floods with hot water because hot water has less air in it. The more air in the ice, the easier it chips away when skated on

- The machine used to resurface the ice is NOT called a Zamboni. Zamboni is a brand name. The technical term for it is an Ice Resurfacing Machine. I drove an Olympia where I worked (the Olympias are made in a town near mine and I went to highschool with the owner's son. Everytime someone in the shop calls it a Zamboni, they have to put $2 into a jar). Each manufacture does things slightly differently and each machine works a little different

- When you see a machine doing a flood, what it is doing is cutting the top layer of ice while also putting down hot water from two different sources. One is called a flood bar; this water comes out a bar with a bunch of holes in it at the back of the conditioner (the big thing the driver sits over). The other comes from wash water which is basically two jets right behind the blade that shoot into the middle. There is a small pump that collects the excess water and returns it to the wash water bin to be reused. This pump also sucks up lint and other small particles.

- The blade used to cut the ice is razor sharp. If you ran your finger across a fresh blade, you wouldn't have a finger anymore (i've seen it happen). You lower and raise the blade to cut off the top layer of ice. The reason NHL rinks and most CHL rinks use two machines isn't because it gives the ice more time to freeze. It's so A) they can drive slower. The slower you drive, the more water you can put down and the less ruts you have and B) because the bin on a machine is only so big. After 20minutes of the best players on the planet playing on the ice, you need to cut off a decent amount of ice so you leave it smooth without ruts and chips. If they only used one machine, the bin would fill up to fast.

- You don't make anything cold (this is true of all refrigeration), you just remove the heat from it. In an ice rink you use two refrigerants, one is called a primary refrigeration. Most rinks these days use ammonia though some still use freon. This kind of refrigerant changes state from liquid to gas to liquid with in the system and by doing so, lets the heat off outside. Those towers you see at the back of rinks are called condensers and the "smoke" they give off is really just straight up steam/heat. The secondary refrigerant is usually brine. Basically salt water or sometimes glycol. This refrigerant never changes state and is pumped through pipes under the playing surface where it pulls heat from the floor and returns into a chiller where that heat is transferred to the primary refrigerant.

I could explain exactly how it all works but that's the jist of it.